The present invention is generally directed to reduced basis weight wrapping papers for use in smoking articles, which result in a reduction in carbon monoxide delivery from said article, and to a method of producing the wrapping papers.
Smoking articles such as cigarettes are conventionally made by wrapping a column of tobacco in a white wrapping paper. At one end, the smoking article usually includes a filter through which the article is smoked. Filters are attached to smoking articles using a tipping paper that is glued to the white wrapping paper. The wrapping papers and tipping papers used to construct smoking articles are typically make from flax or other cellulosic fiber and contain a filler, such as sodium carbonate.
Besides being used to hold the cigarette together, cigarette wrapping papers and tipping papers also contribute to and control many physical properties and characteristics of the cigarette. For instance, cigarette wrapping paper affects the rate at the rate at which the cigarette burns, the number of puffs per cigarette and the total tar delivery per puff. Another property of the cigarette that is affected by the wrapper is the appearance and the characteristics of the ash that is formed as the cigarette burns. Cigarette paper can even be used to limit the amount of smoke that emanates from the lit end of a cigarette when it is left burning and to reduce the tendency of a cigarette to ignite adjacent surfaces.
In the past, wrapping paper opacity was determined primarily as a function of the amount of filler incorporated into the papers. In general, opacity levels are increased as the amount of filler added to the paper is increased. Unfortunately, however, increasing filler levels to increase opacity can adversely affect other characteristics of the paper. For example, increasing filler levels can decrease the strength of the paper. Altering filler levels can also affect the permeability of the paper, which may in turn affect the burn properties of the paper. As such, there is increasing pressure within the industry to keep filler levels in cigarette paper within preset ranges, severely restricting viable methods for increasing paper opacity.
Currently, focus has also been placed upon decreasing the basis weight of wrapping papers in order to decrease the amount of material needed to produce the papers. By reducing the basis weight of wrapping papers, however, two problems can result. First, by reducing the basis weight, the opacity of the wrapping paper is simultaneously decreased causing the paper to aesthetically decline in appearance by unmasking the cigarette""s contents. Decreasing the basis weight of the wrapping papers can also cause a decrease in the tensile strength of the paper.
Due to the above limitations, it has been extremely difficult to create a wrapping paper with a decreased basis weight while maintaining an opacity and tensile strength level that is commercially acceptable.
In addition to decreasing the basis weight of wrapping papers, many attempts have also been made to reduce various constituents contained in the smoke of a smoking article. For instance, although carbon monoxide levels present in smoke emanating from a smoking article are relatively low, a need currently exists for a method for reducing the levels even further. Such reduced levels may be necessary in the future in order to meet government regulations, such as in Europe or in the United States.
The present invention recognizes and addresses the foregoing disadvantages, and others of prior art constructions and methods.
In general, the present invention is directed to wrapping papers of reduced basis weight and carbon monoxide delivery for use in smoking articles that retain the opacity and tensile strength levels commercially required. According to the present invention, the reduced basis weight wrapping papers contain a white pigment and optionally black pigment.
Accordingly, it is an object of the present invention to provide a paper of reduced basis weight and carbon monoxide delivery that can be used as an outer wrapper for smoking articles.
These and other objects of the present invention are achieved by providing a wrapping paper for a smoking article. The wrapping paper includes a paper substrate containing at least one filler. In accordance with the present invention, in order to reduce carbon monoxide delivery of a smoking article incorporating the wrapping paper, the wrapping paper has a fiber basis weight of less than about 18 gsm, particularly less than about 16.5 gsm, and more particularly less than about 15 gsm. When incorporated into a smoking article, the smoking article can have a carbon monoxide delivery of less than about 18 mg per smoking article particularly less than about 17 mg per smoking article, and more particularly less than about 15 mg per smoking article.
As long as the wrapping paper has a low fiber basis weight, the total weight of the wrapping paper can vary depending on the particular application. For instance, by adding significant amounts of fillers, the wrapping paper can have a basis weight up to about 30 gsm, particularly less than about 25 gsm, and, in one embodiment, can have a basis weight of less than about 22 gsm. At lower basis weights, wrapping papers can be made in accordance with the present invention that have sufficient opacity properties and tensile strength properties for practical use in commercial applications.
When constructing low basis weight wrapping papers in accordance with the present invention, the wrapping papers can include a white pigment having a median particle size of from about 0.1 microns to about 0.5 microns, and more particularly from about 0.2 microns to about 0.4 microns. Within this particle size range, the white pigment possesses more efficient light scattering characteristics than other conventional fillers.
Optionally, a second filler can be incorporated into the paper wrapper. The second filler comprises a black pigment, which can be present within the paper substrate in an amount up to about 2% by weight and particularly from about 0.1% to about 1.0% by weight.
The white pigment can be, for instance, precipitated calcium carbonate (PCC), titanium dioxide, or mixtures thereof, while the black pigment can be carbon, iron oxide, or mixtures thereof. The total filler content within the paper substrate can be from about 15% to about 40% by weight, and particularly from about 20% to about 30% by weight. In this embodiment, the wrapping paper can have a basis weight from about 14 g/m2 to about 22 g/m2, and in particular from about 17 g/m2 to about 20 g/m2.
The permeability of wrapping papers made in accordance with the present invention can be from about 5 Coresta units to about 80 Coresta units, and in particular from about 15 Coresta units to about 55 Coresta Units.
Through the use of the fillers described above, paper wrappers having a relatively low basis weight can be made having reduced carbon monoxide delivery while maintaining an acceptable opacity and tensile strength. In particular, the fillers can be incorporated into the paper in a manner so as to maintain the opacity of the paper in an amount of at least 70%. The tensile strength of the paper, on the other hand, can be at least 1800 g/29 mm, and particularly at least 2000 g/29 mm.
The present invention is also directed to smoking articles containing a column of smokable filler. The column of smokable filler is surrounded by a wrapping paper of reduced fiber basis weight and carbon monoxide delivery.
Other features and aspects of the present invention are discussed in greater detail below.